The head of the UN's World Food Programme (WFP) today called for global action to tackle the "silent tsunami" of the world food crisis.

Josette Sheeran, executive director of the WFP, said international action is needed to respond in the same way nations reacted to the boxing day tsunami in 2004. If nothing is done, 100 million people face being plunged into hunger, Sheeran warned.

Speaking ahead of a summit on food prices, she said: "This is the new face of hunger - the millions of people who were not in the urgent hunger category six months ago but now are.

"The response calls for large-scale, high-level action by the global community, focused on emergency and longer-term solutions."

Sheeran said high food prices were pushing the world's poor further into poverty and the effect on nutrition "will hurt children for a lifetime".

The WFP has already been forced to suspend school feeding for 450,000 Cambodian children.

Sheeran insists that unless there is a coordinated response to the food crisis involving governments, other UN agencies, the World Bank, International Monetary Fund and other humanitarian groups, further cuts will be necessary.

The prime minister, Gordon Brown, is also attending today's summit in London.

Writing on the Downing Street website earlier today, he said hunger was now the globe's number one threat to public health and a "moral challenge" for everyone.

He wrote: "Tackling hunger is a moral challenge to each of us and it is also a threat to the political and economic stability of nations.

"So I believe we need to see a fully coordinated response by the international community."

The international development secretary, Douglas Alexander, who is chairing today's meeting, said the government would provide the WFP with an extra £30m as part of a £455m aid package to help tackle the crisis.

Spending on agricultural research will be boosted by £400m over five years and £25m more targeted on boosting the incomes of the world's poorest people.

Alexander said: "There is no simple answer to this global situation. As part of the UK's response, we will work with key international institutions, such as the World Bank, IMF and UN, to develop a comprehensive approach that will help put food on the table for nearly a billion people going hungry across the world."

The summit is also discussing an EU policy on the use of biofuels. Brown has already implied that the UK's enthusiasm for biofuels may be waning.

He wrote said that the government will need to be "more selective in our support" for biofuels, amid concerns that using farmland for the energy crops is contributing to the surge in global food prices.

"Not only are biofuels pushing up food prices, but they are also linked to human rights abuses and land-grabs from the poor," he said.

"The government must not only change policy in the UK but take a lead in Europe and ensure that no further targets are set by the commission."

Friends of the Earth's food campaigner Vicky Hird said: "Food production must be revolutionised to prevent a global catastrophe. We must stop putting the profits of agri-business ahead of the welfare of millions of poor people around the world."

Today's summit brings together international organisations such as the WFP and African Development Bank with campaigners like Oxfam and Save the Children, consumer bodies and players in the food chain like the National Farmers Union and Sainsbury's.

The groups are aiming to develop a plan to present to the EU in June, the G8 in July and a special meeting of the UN in September.